The present invention relates to a communication network system including relaying stations for inter-connecting a plurality of networks. More particularly, the invention is concerned with a communication network system in which exchange or transfer of route information between or among the relaying stations is suspended, i.e., dynamic routing mode is changed over to static routing mode, when predetermined conditions are satisfied.
In the relaying control carried out by the relaying station (which may also be referred to as the repeater station) in the communication system such as mentioned above, there is adopted a dynamic routing control, a static routing control or a hybrid control corresponding to combination of both the above-mentioned controls.
A dynamic routing process is described, for example, in T. Tanimura's "Practical Techniques Of UNIX-LAN Architecture" published by Soft Research Center Company of Japan, p. 221.
Parenthetically, with the terms "dynamic routing", it is contemplated to mean such a system or scheme in which the relaying stations exchange route information (i.e., information concerning the routes via which communication data are to be transferred) with one another periodically at a predetermined time interval, wherein in each of the relaying stations, the route information as updated by the exchange is recorded in a route information table provided in each station together with information concerning the times of the exchange.
On the other hand, a static routing process is also described in the same literature as mentioned above (see p. 219).
According to the static routing scheme, the route information is set up by the user and registered in an associated routing table without exchanging the route information among the relaying stations. Thus, predetermined routes are always selected.
In general, the route information used in the static routing is registered by the manager or user of the relaying station. Upon registration, the route information for the destinations is searched and inputted manually, whereupon effectiveness of the route information is checked or confirmed.